Average Weather In April For San Juan, Puerto Rico

Location

This report describes the typical weather at the Luis Muñoz Marín International Airport (San Juan, Puerto Rico) weather station over the course of an average April. It is based on the historical records from 1992 to 2012. Earlier records are either unavailable or unreliable.

San Juan has a tropical rainforest climate with no dry season. The area within 25 mi of this station is covered by oceans and seas (48%), forests (30%), grasslands (12%), marshes (6%), and croplands (3%).

Temperature

The month of April is characterized by essentially constant daily high temperatures, with daily highs around 85°F throughout the month, exceeding 89°F or dropping below 81°F only one day in ten.

Daily High and Low Temperature in April

The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
Daily low temperatures are around 74°F, falling below 71°F or exceeding 77°F only one day in ten.

Fraction of Time Spent in Various Temperature Bands in April

The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

Sun

Over the course of April, the length of the day is essentially constant. The shortest day of the month is April 1 with 12:20 hours of daylight; the longest day is April 30 with 12:48 hours of daylight.

Daily Hours of Daylight and Twilight in April

The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

The earliest sunrise is at 5:57am on April 30; the latest sunset is at 6:46pm on April 30; the latest sunrise is at 6:18am on April 1; the earliest sunset is at 6:37pm on April 1.

Daylight savings time (DST) is not observed in 2012.

Daily Sunrise & Sunset with Twilight in April

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray.

Clouds

The median cloud cover is 43% (partly cloudy) and does not vary substantially over the course of the month.

Median Cloud Cover in April

The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

On April 15, a representative day, the sky is clear or mostly clear 45% of the time, partly cloudy 30% of the time, and mostly cloudy or overcast 24% of the time.

Cloud Cover Types in April

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around April 27, occurring in 59% of days. Precipitation is least likely around April 1, occurring in 55% of days.

Probability of Precipitation at Some Point in the Day in April

The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

Throughout April, the most common forms of precipitation are light rain, heavy rain, moderate rain, and thunderstorms.

Light rain is the most severe precipitation observed during 56% of those days with precipitation. It is most likely around April 3, when it is observed during 33% of all days.

Heavy rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around April 24, when it is observed during 11% of all days.

Moderate rain is the most severe precipitation observed during 16% of those days with precipitation. It is most likely around April 7, when it is observed during 9% of all days.

Thunderstorms are the most severe precipitation observed during 11% of those days with precipitation. They are most likely around April 30, when it is observed during 9% of all days.

Types of Precipitation Throughout April

Relative frequency of various types of precipitation over the course of a typical April.

Snow

Either snow is exceptionally unlikely to fall at this location in April or this station does not reliably report precipitation types.

Humidity

The relative humidity typically ranges from 58% (mildly humid) to 89% (very humid) over the course of a typical April, rarely dropping below 49% (comfortable) and reaching as high as 97% (very humid).

The air is driest around April 1, at which time the relative humidity drops below 64% (mildly humid) three days out of four; it is most humid around April 28, rising above 86% (very humid) three days out of four.

Relative Humidity in April

The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

Dew Point

Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.

Over the course of a typical April, the dew point typically varies from 66°F (muggy) to 74°F (very muggy) and is rarely below 62°F (mildy humid) or above 76°F (oppressive).

Dew Point in April

The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

Over the course of April typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 21 mph (fresh breeze).

The highest average wind speed of 8 mph (gentle breeze) occurs around April 5, at which time the average daily maximum wind speed is 17 mph (moderate breeze).

The lowest average wind speed of 8 mph (gentle breeze) occurs around April 28, at which time the average daily maximum wind speed is 16 mph (moderate breeze).

Wind Speed in April

The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
The wind is most often out of the east (39% of the time) and north east (17% of the time). The wind is least often out of the north west (1% of the time), west (1% of the time), south west (1% of the time), and north (3% of the time).

Wind Directions in April

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions in April

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.